The present invention relates to a cryptographic key having a pseudo random number generator for generating a pseudo random number of a chaotic time series, an encryption device for encrypting plaintext data by use of the pseudo random number of the chaotic time series from the cryptographic key, an encryption/decryption device for encrypting and decrypting the plaintext data, a cryptographic key management device for managing the cryptographic key, and a decryption device for decrypting cryptographic data.
Recent years, a universal serial bus (USB) has been used as an interface in which the same connector and cable are used coherently for a connection of a personal computer to relatively low-speed peripheral equipment such as a keyboard, a mouse, a speaker, a modem and a printer. In this USB, a data transfer rate between the personal computer and the peripheral equipment is, for example, 1.5 Mbps, which is relatively low-speed.
There has been known an encryption device for encrypting data by use of a personal computer and peripheral equipment, which are in conformity with the standard of the USB as described above. This encryption device is constituted of a key information unit in which key information is registered, and of a personal computer having a cryptographic algorithm, to which the key information unit is attached.
In the key information unit, there is a key information unit in which the key information is registered by a person at the time of purchase thereof, a key information unit in which the key information is registered at the time of shipment thereof from a factory, or the like. Upon being equipped with the key information unit, the personal computer has read out the key information from the key information unit, has created a cipher key from the key information by use of the cryptographic algorithm, and has encrypted plaintext data by use of this cipher key, thus creating cryptographic data.